Data transmission method and automation-communication network

ABSTRACT

In an automation-communication network, at least one distribution node comprises input/output interfaces each connected to at least one network segment. In a first network segment a first subscriber and in a second network segment a second subscriber are arranged. Data are exchanged between the first and the second subscriber by telegrams realized as scheduled telegrams and unscheduled telegrams. The distribution node receives an unscheduled telegram on an input/output interface and sends an unscheduled telegram on a further input/output interface. The distribution node determines a transmission duration for transmission of the unscheduled telegram. The distribution node transmits the unscheduled telegram. Prior to transmission, the distribution node deposits a first telegram information in a data field. The distribution node fragments the unscheduled telegram if the telegram cannot be transmitted within a time slot. Prior to transmission of the unscheduled telegram, the distribution node enters a second telegram information into the data field.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT Application PCT/EP2019/054661filed Feb. 26, 2019, and German Patent Application DE 10 2018 112 357.4,filed May 23, 2018, each of which is incorporated by reference herein,in the entirety and for all purposes.

FIELD

The present invention relates to a method for transmitting data in anautomation-communication network. The invention furthermore relates toan automation-communication network that is configured for transmittingdata and to a distribution node that is suitable for executing thedata-transmission method.

BACKGROUND

A so-called local area network (LAN) is a spatially limited network inwhich various network components are coupled to one another. The networkcomponents may be one or a plurality of servers and work stations,so-called nodes, that are connected to one another via communicationlines in the form of coaxial, optical-fiber or twisted-pair cables.Communication between the network components within the LANs is carriedout on the basis of network protocols.

In this context, the Ethernet protocol is the most widespread standardof network protocols for an LAN. Ethernet telegrams may comprise auser-data block with a length of 1500 bytes and allow fortelegram-transmission rates between the individual network componentswithin the LAN of several Gigabytes per second wherein the telegrams aretransmitted in a package-oriented manner. The Ethernet protocol is alsoused in industrial production plants in the form of the so-called“Industrial Ethernet”. In automation technology, the Ethernet protocolmay e.g. serve to control data exchange in manufacturing, building andprocess automation with regard to control tasks and to guarantee thereal-time capability of the system.

The automation-communication networks used in automation technologygenerally correspond to so-called “field-bus systems”. Field-bus systemsare bus systems in which distributed devices of a machine periphery suchas input and/or output modules, drives and operational terminals areconnected to control units via the bus system. A shared transmissionchannel (e.g. as a field bus or radio link) is provided for exchangingdata. If a plurality of subscribers send telegrams at the same time, apossibility has to be provided for the subscribers of sharing thetransmission channel in mutual consent. One such possibility is usingthe “master-slave principle”.

Usually, the control units at the field bus are the active bussubscribers, in the following referred to as “master subscribers”. Themaster subscribers are provided with the access rights of the field-bussystem and determine the data flow on the field bus in the form oftelegrams. The passive field-bus subscribers, in the following referredto as “slave subscribers”, mostly correspond to the peripheral machinedevices. The slave subscribers do not have access rights and may onlyacknowledge received data or, respectively, telegrams or transmit dataor, respectively, telegrams upon request by the master subscriber.

Distribution nodes that are also referred as “switches” are frequentlyused in automation-communication networks in order to connect theindividual network segments having network components to one another andto ensure that the data or, respectively, telegrams within the networksegments quickly reach their destination. The telegrams to betransmitted in the automation-communication network may be cyclicreal-time telegrams that are relevant for controlling the automationsystem and comprise cyclic input/output data of the subscribers, andacyclic non-real-time telegrams that e.g. comprise parameters or statusdata of the subscribers. Cyclic real-time telegrams are in generalscheduled telegrams having a fixed transmission time for beingtransmitted by the distribution nodes, whereas acyclic non-real-timetelegrams frequently occur in the telegram flow in an unscheduled mannerand do not have a fixed transmission time for being transmitted.

In order to forward the scheduled cyclic real-time telegrams, aswitching table, a so-called “routing list”, is deposited in thedistribution node that e.g. comprises a telegram identification, e.g. inthe form of a MAC address, an input/output interface and a transmissiontime. In contrast to the described “routing list” for the scheduledcyclic telegrams, the “routing list” for the unscheduled acyclicnon-real-time telegrams does not comprise a transmission time as theunscheduled acyclic telegrams do not have a transmission time.

In order to ensure that the forwarding of non-real-time telegrams thatwill in the following be referred to as unscheduled telegrams will notdelay the forwarding of real-time telegrams that will in the followingbe referred to as scheduled telegrams, a data-transmission cycle for thetelegrams is divided up into three time sections in the distributionnode of U.S. Pat. No. 8,179,923 B2.

In a first time section, the so-called “cyclic time section”, onlyscheduled telegrams may be received and forwarded. In the subsequentsecond time section referred to as “acyclic time section”, theunscheduled telegrams are transmitted. In the third and last timesection, the so-called “transitional time section”, acyclic telegramscan further be received, but must not be forwarded.

The transitional time section that at least corresponds to the maximumforwarding time for an unscheduled telegram prevents that a delayedtransmission of scheduled telegrams occurs in the subsequent cyclic timesection due to the forwarding of an unscheduled acyclic telegram stillbeing in process. The unscheduled acyclic telegrams received in thetransitional time section are buffered in the distribution node andtransmitted in the next acyclic time section.

In the distribution node, an overload of unscheduled telegrams mayeasily occur because each distribution node may transmit unscheduledtelegrams outside of the cyclic time section, e.g. within the acyclictime section, in an uncontrolled manner. Such overloads particularlyoccur when the acyclic time section in the telegram or, respectively,data-transmission cycle is considerably shortened compared to the cyclictime section. Due to the operating times within theautomation-communication network and in order to achieve down times thatare as short as possible during telegram or, respectively, datatransmission, the scheduled telegrams are frequently not transmitteddirectly one after the other in the cyclic time section, but withintermediate time gaps. As a result, the cyclic time section extends. Insuch a case, there is a danger of the receiving buffer for theunscheduled telegrams in the distribution node overflowing if too manyunscheduled telegrams are received in the transitional time period andin the acyclic time section.

Moreover, according to the procedure described in U.S. Pat. No.8,179,923 B2, the automation-communication network comprising thedistribution node has to be previously set up during a configurationphase. If changes occur in the scheduled telegrams that are transmittedin the cyclic time section, a new configuration has to be generated andstored in the distribution node. If a plurality of distribution nodes isused in the automation-communication network, the new configuration hasto be additionally transmitted to the distribution nodes. This meansthat such a change in the configuration may take up severaldata-transmission cycles. In U.S. Pat. No. 8,179,923 B2, the unscheduledtelegrams may only be transmitted in the acyclic phase. An unscheduledtelegram is then fully transmitted in the time slot in which noscheduled telegrams are transmitted. However, the disadvantage of themethod of U.S. Pat. No. 8,179,923 B2 is that the unscheduled telegramhas to have a length that at most corresponds to the remaining time slotuntil the next scheduled telegram is transmitted so that the acyclictelegram can be transmitted within this free time slot.

SUMMARY

A method for transmitting data in an automation-communication networkhaving at least one distribution node provides an efficient throughputof telegrams in the distribution node, in particular of unscheduledtelegrams, furthermore an improved automation-communication network.

EXAMPLES

According to one aspect, a method for transmitting data in anautomation-communication network having at least one distribution nodeis provided. The distribution node comprises a plurality of input/outputinterfaces that are each connected to at least one network segment,wherein in a first network segment in the automation-communicationnetwork a first subscriber and in a second network segment a secondsubscriber are arranged. A data exchange between the first subscriberand the second subscriber is carried out in the form of telegrams,wherein the telegrams are realized as scheduled telegrams characterizedby a fixed transmission time for transmission by the at least onedistribution node, and as unscheduled telegrams characterized by nothaving a fixed transmission time for transmitting by the at least onedistribution node. The unscheduled telegrams are each assigned controldata for the distribution node and the control data have a data fieldthat is processed by the distribution node. The distribution node isconfigured to receive the unscheduled telegram on an input/outputinterface and to send it on a further input/output interface. Moreover,the distribution node is configured to determine a transmission durationfor transmitting the unscheduled telegram and to determine a time slotof the input/output interface remaining until transmission of a nextscheduled telegram, wherein the input/output interface is provided asthe transmission interface for the unscheduled telegram. Furthermore,the distribution node examines whether the telegram with thetransmission duration can be transmitted within the remaining time slot.The distribution node is configured to transmit the unscheduled telegramvia the transmission interface if the unscheduled telegram having thetransmission duration can be transmitted within the time slot of thetransmission interface remaining until transmission of the nextscheduled telegram. Prior to transmitting the unscheduled telegram, thedistribution node enters a first telegram information into the datafield of the control data of the telegram. The first telegraminformation indicates that the unscheduled telegram is transmitted infull. The distribution node is moreover configured to fragment theunscheduled telegram if the telegram having the transmission durationcannot be transmitted within the time slot of the transmission interfaceremaining until transmission of the next scheduled telegram.Furthermore, the distribution node enters a second telegram informationinto the data field of the control data of the unscheduled telegramprior to transmitting the unscheduled telegram, wherein the secondtelegram information indicates that the unscheduled telegram is going tobe fragmented and comprises an additional distribution-nodeidentification that serves to discern the individual distribution nodesin the automation-communication network.

According to another aspect, an automation-communication network havingat least one distribution node is provided. The distribution nodecomprises a plurality of input/output interfaces that are each connectedto at least one network segment, wherein in a first network segment afirst subscriber and in a second network segment a second subscriber arearranged. Data are exchanged between the first subscriber and the secondsubscriber in the form of telegrams. The telegrams are realized asscheduled telegrams characterized by a fixed transmission time fortransmitting via the at least one distribution node and as unscheduledtelegrams characterized by not having a fixed transmission time fortransmitting via the at least one distribution node. The unscheduledtelegrams are each assigned control data for the distribution node andthe control data comprise a data field that is processed by thedistribution node. The distribution node is configured to receive anunscheduled telegram on an input/output interface and to send anunscheduled telegram on a further input/output interface. Thedistribution node is further configured to determine a transmissionduration for transmission of the unscheduled telegram. Also thedistribution node is configured to determine a time slot of theinput/output interface provided as the transmitting interface for theunscheduled telegram, said time slot remaining until a next scheduledtelegram is transmitted, and to examine whether the unscheduled telegramwith said transmitting duration can be transmitted within the remainingtime slot. The distribution node is moreover configured to transmit theunscheduled telegram via the transmission interface if the unscheduledtelegram with said transmission duration can be transmitted within theremaining time slot of the transmitting interface until the nextscheduled telegram is transmitted. Furthermore the distribution node isconfigured to enter a first telegram information prior to thetransmission of the unscheduled telegram into the data field of thecontrol data of the unscheduled telegram, wherein the first telegraminformation indicates that the unscheduled telegram is fullytransmitted. The distribution node is configured to fragment theunscheduled telegram if the telegram with the transmission durationcannot be transmitted within the remaining time slot of the transmissioninterface up until transmission of the next scheduled telegram. Thedistribution node is moreover configured to enter a second telegraminformation in the data field of the control data of the unscheduledtelegram prior to transmitting the unscheduled telegram, wherein thesecond telegram information indicates that the telegram is going to befragmented and comprises an additional distribution-node identificationthat serves to discern the individual distribution nodes in theautomation-communication network.

According to another aspect, a distribution node for anautomation-communication network is provided. The distribution nodehaving a plurality of input/output interfaces that are each connected toat least one network segment, wherein in a first network segment a firstsubscriber and in a second network segment a second subscriber arearranged. Data are exchanged between the first subscriber and the secondsubscriber in the form of telegrams. The telegrams are realized asscheduled telegrams characterized by a fixed transmission time fortransmitting via the at least one distribution node and as unscheduledtelegrams characterized by not having a fixed transmission time fortransmitting via the at least one distribution node. The unscheduledtelegrams are each assigned control data for the distribution node andthe control data comprise a data field that is processed by thedistribution node. The distribution node is configured to receive anunscheduled telegram on an input/output interface and to send anunscheduled telegram on a further input/output interface. Furthermorethe distribution node is configured to determine a transmission durationfor transmitting the unscheduled telegram. Moreover the distributionnode is configured to determine a time slot of the input/outputinterface provided as the transmitting interface for the unscheduledtelegram, said time slot remaining until a next scheduled telegram istransmitted, and to examine whether the unscheduled telegram with saidtransmitting duration can be transmitted within the remaining time slot.The distribution node transmits the unscheduled telegram via thetransmission interface if the unscheduled telegram with saidtransmission duration can be transmitted within the remaining time slotof the transmitting interface until the next scheduled telegram istransmitted. The distribution node also enters a first telegraminformation prior to the transmission of the unscheduled telegram intothe data field of the control data of the unscheduled telegram, whereinthe first telegram information indicates that the unscheduled telegramis fully transmitted. The distribution node fragments the unscheduledtelegram if the telegram with the transmission duration cannot betransmitted within the remaining time slot of the transmission interfaceup until transmission of the next scheduled telegram. The distributionnode enters a second telegram information in the data field of thecontrol data of the unscheduled telegram prior to transmitting theunscheduled telegram, wherein the second telegram information indicatesthat the telegram is going to be fragmented and comprises an additionaldistribution-node identification that serves to discern the individualdistribution nodes in the automation-communication network.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described properties, features and advantages as well as themanner in which they are achieved will become clearer and better tounderstand in context with the following description of embodimentexamples that will be explained in more detail in conjunction with theschematic drawings, in which:

FIG. 1 shows a schematic design of an automation-communication networkhaving a plurality of distribution nodes and network segments;

FIG. 2A depicts a schematic principle of an unscheduled telegram forexchanging data between the first subscriber and the second subscriberin the automation-communication network shown in FIG. 1, wherein threedistribution nodes are arranged between the two subscribers andtransmission of the unscheduled telegram is shown on the forward run tothe second subscriber; and

FIG. 2B depicts a schematic principle of an unscheduled telegram forexchanging data between the first and the second subscriber in theautomation-communication network shown in FIG. 1, wherein threedistribution nodes are arranged between the two subscribers and thetransmission of the unscheduled telegram that is divided up intotelegram fragments is shown on the way back to the first subscriber.

DETAILED DESCRIPTION

In conjunction with the following figures, examples of a method fortransmitting data in an automation-communication network, e.g. usedwithin the framework of manufacturing, building and process automation,are described. In this context, the indication of use is not to beconsidered limiting; other areas of an automation-communication networkmay be used in which a first subscriber is arranged in a first networksegment, a second subscriber is arranged in a second network segment andat least one distribution node is arranged between the two subscribers.

It is to be noted that the figures are only schematic and not drawn toscale. Hence, components and elements shown in the figures may bedepicted excessively large or reduced for a better understanding.Moreover, it is to be noted that the reference numerals in the figuresremain unchanged if they refer to identically embodied elements and/orcomponents and/or quantities.

Automation-communication networks are generally realized as field-bussystems in which the subscribers are interlinked via the field bus. Thesubscribers may exchange data with control units, wherein usuallyreal-time-capable network protocols are used for this purpose. Dataexchange between the subscribers on the field bus is frequentlycontrolled according to a master-slave-administration principle. Theactive bus subscribers that are also referred to as master subscriberscorrespond to the control units that determine and coordinate datatransmission on the field bus. The passive bus subscribers that arereferred to as slave subscribers and do not have bus-access rights, onthe other hand, are the devices of the machine periphery. Thereby, apassive bus subscriber may simply receive messages, acknowledge them andtransmit data or, respectively, telegrams upon request by the mastersubscriber. The devices of the machine periphery may e.g. correspond toinput and/or output components that connect the sensors or actuators ofa machine or plant to one another via the field bus. Alternatively, theinput and/or output components may be directly integrated into thesensors or actuators of the machine or of the plant.

In automation technology, a cyclic control process may be triggered bythe master subscriber and be carried out by means of a data exchangebetween the master subscriber and the slave subscriber via the fieldbus. For this purpose, the master subscriber transmits the output dataas scheduled telegrams on the field bus, wherein the slave subscriberextracts the output data assigned to it from the telegram in order toprocess the output data to result in data that, in turn, are transmittedback to the master subscriber and serve as input data for the mastersubscriber in the next cyclic control process. Such scheduled telegramsare also referred to as “cyclic telegrams” or, respectively, as“real-time telegrams”.

Apart from real-time telegrams that are relevant when carrying outcontrol tasks, unscheduled so-called “acyclic telegrams” are transmittedon the field bus, as well. Unscheduled telegrams are telegrams that arenot cyclically repeated on the field bus and are thus notreal-time-relevant. For example, these telegrams may compriseparameterization and configuration data or diagnosis information.Acyclic telegrams are for this reason also referred to as “non-real-timetelegrams”.

Field-bus systems the administrative structure of which is based on themaster-slave principle may be operated by various network protocols. TheEthernet protocol, for example, represents the most wide-spread standardof network protocols for a local network (LAN). Ethernet telegrams maycomprise a user-data block having a length of 1500 bytes and allow fortelegram-transmission rates between the individual network componentswithin the LANs of several gigabytes/second. The Ethernet protocol isused in industrial manufacturing plants or machines of an automationsystem, as well, in the form of the so-called “Industrial Ethernet”,wherein the Ethernet protocol is in this context supposed to guaranteethe real-time demands of the automation system. The EtherCAT protocol,for example, is such a protocol that is based on the Ethernet-protocoltechnology and may be used in real-time-capable automation systems.

The special feature of the EtherCAT protocol is that the processing ofuser data in the user-data block of the EtherCAT telegram that maycomprise the above-mentioned scheduled or, respectively, unscheduledtelegrams is carried out by the slave subscriber already during telegramcirculation. In this manner, quick data processing may be provided inthe automation-communication system by the EtherCAT protocol, which maye.g. be advantageously used for real-time systems.

The EtherCAT telegram comprises datagrams which each comprise acontrol-data field and a user-data field. The control-data fieldcomprises a command field which informs the slave subscriber on themanner in which it is to process the user data of the scheduled or,respectively, unscheduled telegram: for example, whether the slavesubscriber is to insert data into the user-data field of the scheduledor, respectively, unscheduled telegram in a writing operation, orwhether it should at first extract data from the user-data field andsubsequently insert data into the user-data field in a write/readoperation, or, respectively, whether the slave subscriber should onlyextract data from the user-data field in a read operation. Moreover, thecontrol-data field comprises an address field. In the address field, thedata area in the slave subscriber is determined by mean of which theslave subscriber is to exchange data during circulation of the user datafield.

After receiving the control-data field in the datagram of the EtherCATtelegram, the slave subscriber starts to evaluate the command field orthe address field. If the slave subscriber is addressed, it extracts theoutput data intended for it from the user-data field in case of a reador, respectively, write/read datagram, while the datagram in theEtherCAT telegram circles through the slave subscriber. If the datagramis a write or, respectively, a write/read datagram, the correspondingslave subscriber inserts the input data in the user-data field in thedatagram during circulation. Processing the circling datagrams by theslave subscribers only minimally delays the EtherCAT telegram.

The following will be described in conjunction with theEtherCAT-telegram circulation. However, any other Ethernet protocolapplicable in real-time systems may be used. Moreover, the method may berealized with a standard Ethernet protocol. Likewise, it is possible touse a non-Ethernet-based automation-communication network in which afirst subscriber is arranged in a first network segment and a secondsubscriber is arranged in a second network segment as well as at leastone distribution node comprising a plurality of input/output interfaces,furthermore not limited to an automation network having a hierarchicalmaster-slave-administration structure.

In the automation-communication network, the individual network segmentswith subscribers are connected to one another by one or a plurality ofdistribution node(s) that may be realized as so-called “switches”. Thedistribution nodes further serve to coordinate the data exchange of thesubscribers in the network segments as scheduled cyclic and unscheduledacyclic telegrams and to forward the scheduled and unscheduled telegramsto their destination on time. The corresponding distribution nodescomprise a plurality of input/output interfaces which are each connectedto at least one network segment, wherein in a first network segment afirst subscriber and in a second network segment a second subscriber isarranged. The distribution node is configured to receive the scheduledand unscheduled telegrams on an input/output interface and to transmitthem on a further input/output interface.

The scheduled and unscheduled telegrams are each assigned control datafor the respective distribution node. They comprise a data field that isprocessed by the respective distribution node. Before the respectivedistribution node transmits an unscheduled telegram, the distributionnode determines a transmission duration for transmitting thecorresponding unscheduled telegram. In addition, the respectivedistribution node determines a time slot of the input/output interfaceof the distribution node provided as transmission interface for theunscheduled telegram, said time slot remaining until the next scheduledtelegram is transmitted.

Due to stored information on the scheduled telegrams, the transmissiontimes that are usually determined by the first subscriber, the mastersubscriber, for the individual distribution nodes, the distributionnodes know how long a corresponding data-transmission path to thesuperordinate distribution nodes is going to remain free, e.g. on theway back. This means that time slots of the transmission interface ofthe corresponding distribution node remaining until the next scheduledtelegram is sent are known or, respectively, may be determined in asimple manner in order to decide whether the unscheduled telegram withthe transmission time can be transmitted within the above-mentioned timeslot of the transmission interface of the distribution node in full ordivided up into fragments.

If the corresponding distribution node has determined both time values,it examines whether the unscheduled telegram with the respectivetransmission duration can be transmitted within the time slot remaininguntil the next scheduled telegram of the transmission interface of thedistribution node is sent. If this is the case, the distribution nodetransmits the unscheduled telegram in full. In addition, thedistribution node inserts a first telegram information into the datafield of the control data of the unscheduled telegram that indicatesthat the unscheduled telegram is fully transmitted. If the result of thedistribution node's examination, however, is that the unscheduledtelegram with the time duration cannot be transmitted within the timeslot of the transmission interface remaining until the next scheduledtelegram is sent, the respective distribution node fragments theunscheduled telegram.

Moreover, the respective distribution node inserts a second telegraminformation into the data field of the control data of the unscheduledtelegram prior to transmission, wherein the second telegram informationindicates that the unscheduled telegram has been fragmented and itcomprises an additional distribution-node identification that serves todiscern the individual distribution nodes if a plurality of distributionnodes for connecting the network segments is arranged in theautomation-communication network. Furthermore, the first telegraminformation in the data field of the control data of the unscheduledtelegram may comprise the distribution-node identification of therespective distribution node.

Fragmenting the telegrams is usually on the way back of the telegramcirculation, because on the forward run the first subscriber, i.e. themaster subscriber, determines in the first network segment when thescheduled telegrams may be transmitted via the distribution node to thesecond subscriber, the slave subscriber in the second network segment.Due to this determination, telegram collisions may be avoided. This is,however, different when the scheduled or, respectively, unscheduledtelegrams are sent on the way back from the slave subscriber to themaster subscriber. In this context, collisions may be prevented of therespective distribution node examines whether the time slot of thetransmission interface of the distribution node remaining untiltransmission of the next scheduled telegram is sufficient for sendingthe unscheduled telegram with the transmission duration in order totransmit the unscheduled telegram fully or, as the case may be, dividedup into fragments if the corresponding data-transmission path happens tobe free.

By means of the proposed procedure, the telegram circulation in theautomation-communication network may be optimized. In this context, themain idea is the optimal utilization of the time slot of thetransmission interface of the distribution node for transmission of theunscheduled telegram that remains until transmission of the nextscheduled telegram. This is possible because the distribution nodes knowdue to the stored transmission times of the scheduled telegrams how longthe respective data-transmission path to the next distribution node isgoing to remain free. As a result, the unscheduled telegram may betransmitted in said remaining time slot without affecting circulation ofthe scheduled telegram. Thus, the present method, theautomation-communication network and the distribution node areadvantageously suitable for transmitting the unscheduled acyclictelegrams since in this manner, the existing capacity for transmittingof those telegrams may be used in the best possible way. Consequently,the proposed method, automation-communication network and distributionnode have the advantage that it reduce the down time in telegramtransmission due to efficient use of the remaining time slot of thetransmission interface of the distribution node to a minimum.

The corresponding distribution node transmits the fragmented unscheduledtelegram via its transmission interface, together with the secondtelegram information it enters into the data field of the control dataof the telegram prior to transmitting the unscheduled telegram. Thesecond telegram information informs other distribution nodes or,respectively, the first subscriber in the automation-communicationnetwork that the fragmented unscheduled telegram is not a completeunscheduled telegram, but that further telegram fragments are necessaryfor completeness. The information that during fragmentation of theunscheduled telegram further telegram fragments are transmitted areinserted into the second telegram information by the correspondingdistribution node, as well.

In addition, the second telegram information in the data field of thecontrol data of the unscheduled telegram allows to discern therespective distribution node in the automation-communication network bythe distribution-node identification. The distribution-nodeidentification moreover allows to assign the individual telegramfragments to an associated unscheduled telegram as the respectivedistribution-node identifications of the distribution nodes for anunscheduled telegram comprising a plurality of telegram fragments do notchange. The distribution-node identification of the individualdistribution nodes is, however, increased with regard to its value for anew unscheduled telegram which is fragmented. Likewise, thedistribution-node identification for a new unscheduled telegram that isnot fragmented is increased. Only in case of a scheduled telegram, thedistribution-node identification is not incremented.

A method for transmitting data in an automation-communication networkhaving at least one distribution node as well as a correspondingautomation-communication network are provided. The distribution nodecomprises a plurality of input/output interfaces that are each connectedto at least one network segment, wherein in a first network segment inthe automation-communication network a first subscriber and in a secondnetwork segment a second subscriber are arranged. A data exchangebetween the first subscriber and the second subscriber is carried out inthe form of telegrams, wherein the telegrams are realized as scheduledtelegrams characterized by a fixed transmission time for transmission bythe at least one distribution node, and as unscheduled telegramscharacterized by not having a fixed transmission time for transmittingby the at least one distribution node. The unscheduled telegrams areeach assigned control data for the distribution node and the controldata have a data field that is processed by the distribution node. Thedistribution node is configured to receive the unscheduled telegram onan input/output interface and to send it on a further input/outputinterface. Moreover, the distribution node is configured to determine atransmission duration for transmitting the unscheduled telegram and todetermine a time slot of the input/output interface remaining untiltransmission of a next scheduled telegram, wherein the input/outputinterface is provided as the transmission interface for the unscheduledtelegram. Furthermore, the distribution node examines whether thetelegram with the transmission duration can be transmitted within theremaining time slot. The distribution node is configured to transmit theunscheduled telegram via the transmission interface if the unscheduledtelegram having the transmission duration can be transmitted within thetime slot of the transmission interface remaining until transmission ofthe next scheduled telegram. Prior to transmitting the unscheduledtelegram, the distribution node enters a first telegram information intothe data field of the control data of the telegram. The first telegraminformation indicates that the unscheduled telegram is transmitted infull. The distribution node is moreover configured to fragment theunscheduled telegram if the telegram having the transmission durationcannot be transmitted within the time slot of the transmission interfaceremaining until transmission of the next scheduled telegram.Furthermore, the distribution node enters a second telegram informationinto the data field of the control data of the unscheduled telegramprior to transmitting the unscheduled telegram, wherein the secondtelegram information indicates that the unscheduled telegram is going tobe fragmented and comprises an additional distribution-nodeidentification.

The automation-communication network may e.g. be used in automationtechnology in order to exchange data or, respectively, scheduled andunscheduled telegrams between the individual network subscribers bydistribution nodes. In this context, the method for transmitting datamay be advantageously used in the automation-communication network asthe distribution node knows—due to stored information on the scheduledtelegrams, the transmission times of which are usually determined forthe individual distribution noes by the first subscriber—how long acorresponding data-transmission path to the superordinate distributionnode is going to be free e.g. on the way back of the unscheduledtelegram from the second to the first subscriber. This means that theremaining time slot of the transmission interface of the respectivedistribution node remaining until transmission of the next scheduledtelegram is known or, respectively, is easy to determine, and as aresult a decision may be taken on whether an unscheduled telegram havingthe transmission duration may be transmitted in full or in fragmentswithin the above-mentioned time slot of the transmission interface ofthe distribution node.

Within the framework of the procedure, the possibility that unscheduledtelegrams that cannot be transmitted back to the subscriber within thetime slot of the transmission interface of the distribution noderemaining until transmission of the next scheduled telegram may befragmented may prove advantageous. For this purpose, the distributionnode inserts a second telegram information into the control data of theunscheduled telegram prior to transmission of the unscheduled telegram,which indicates that the unscheduled telegram has been fragmented. Inaddition, the second telegram information comprises the distributionidentification. If, however, the distribution node does not fragment theunscheduled telegram because the unscheduled telegram with thetransmission duration can be transmitted during the time slot of thetransmission interface of the distribution node remaining untiltransmission of the next scheduled telegram, the distribution nodesgenerates the first telegram information that indicates that theunscheduled telegram is going to be transmitted in full.

Thus, the procedure may allow for an ideal utilization of the potentialfree time slot of the transmission interface of the distribution noderemaining until transmission of the next scheduled telegram and providethe advantage that down time during telegram or, respectively, datatransmission is reduced to a minimum. The overflow danger of thereceiving buffer of the distribution node due to the incomingunscheduled telegrams may additionally be reduced by the fragmentedtransmission of the unscheduled telegrams.

A plurality of distribution nodes can be arranged between the firstsubscriber and the second subscriber. The respective distribution nodeis assigned a separate data field of the control data of the unscheduledtelegram that is independently processed by the respective distributionnode. The respective distribution node fragments the unscheduledtelegram that is transmitted by the second subscriber to the firstsubscriber, if the unscheduled telegram with the respective transmissiontime cannot be transmitted within the time slot of the transmissioninterface remaining for transmission of the next scheduled telegram bythe respective distribution node. In addition, prior to transmitting theunscheduled telegram the respective distribution node inserts a secondtelegram information into the data field of control data of theunscheduled telegram assigned to it, wherein the second telegraminformation indicates that the unscheduled telegram is going to befragmented and comprises an additional distribution-node identification.Subsequently, the respective distribution node transmits the unscheduledtelegram in fragments. By arranging a plurality of distribution nodesbetween the first and the second subscriber, a throughput of unscheduledtelegrams may be reliably controlled in the automation-communicationnetwork and collisions of scheduled and unscheduled telegrams may beprevented in this manner.

Between the first and second subscriber, a plurality of distributionnodes may be arranged which may render transmission of the unscheduledtelegrams more efficient as a result. Each distribution node is thenassigned a corresponding separate data field in the control data of theunscheduled telegram in which the respective distribution node depositsthe first telegram information if it fully transmits the unscheduledtelegram, or, respectively, the second telegram information if thedistribution node fragments the unscheduled telegram. Multiplefragmenting of the unscheduled telegram by various distribution nodes isanother possibility of realizing telegram transmission.

The separate data field assigned to the respective distribution node maybe divided up as desired, wherein the data-field structure may in anautomation-communication network having a plurality of distributionnodes repeat itself for other data fields of further distribution nodes.This on the one hand simplifies programming during implementation of theprocedure and furthermore provides faster processing and transmitting ofthe data within the automation-communication network if the distributionnodes only have to evaluate or, respectively, to supplement the part ofthe control data that is relevant for them.

The distribution-node identification of the second telegram informationcan allow for additional assigning to the corresponding unscheduledtelegram, wherein the distribution node is embodied to increment thedistribution-node identification of the second telegram information fora new unscheduled telegram. Apart from characterizing the respectivedistribution node, the distribution-node identification also serves tocharacterize the corresponding unscheduled telegram, as thedistribution-node identification of the respective distribution nodesdoes not change for several telegram fragments of an unscheduledtelegram. It is, however, incremented for a new unscheduled telegram inthe automation-communication network, with regard to its value, in orderto provide a discerning feature for further unscheduled telegrams. Astelegram transmission may also be realized such that a plurality ofdistribution nodes subdivide the unscheduled telegram into severaltelegram fragments, a high flexibility may be provided by thedistribution-node identification during transmission of the unscheduledtelegram in the automation-communication network as well as easyrecognition of the individual telegram fragments.

The respective distribution node can note a telegram offset in the datafield of the control data of the unscheduled telegram assigned to it, inthe second telegram information, if the respective distribution nodefragments the unscheduled telegram. The telegram offset indicates avalue n that comprises a position of a first user-data block containedin the unscheduled telegram, wherein the first telegram fragmentparticularly has the telegram-offset value n=0. The telegram offsetallows for the subsequent distribution node to which the unscheduledfragmented telegram is sent to quickly determine the position of theuser-data block and thus to start processing the user data promptly. Forthe recipient, the structure of the unscheduled telegram may be easy torecognize by the telegram offset. An unscheduled telegram that has notbeen divided up into telegram fragments may also have thetelegram-offset value n=0.

The respective distribution node can deposit in the data field ofcontrol data of the unscheduled telegram assigned to it, in the secondtelegram information, that more telegram fragments are to be transmittedif the respective distribution node fragments the unscheduled telegram.By depositing the information in the data field of the control data ofthe unscheduled telegram that further telegram fragments are to betransmitted, the subsequent distribution nodes are informed on thefragmenting of the unscheduled telegram. As a result, they know thatfurther telegram fragments may follow the transmitted telegram fragment.This simplifies assembling the telegram fragments on the receiving sideand may increase reliability of the telegram or, respectively, datatransmission.

The telegrams can be transmitted on a closed data-transmission path,starting from the first subscriber to the second subscriber on theforward run, and on the way back starting from the second subscriber tothe first subscriber. The first subscriber arranged in the first networksegment is realized as a master subscriber and the second subscriberarranged in the second network segment is realized as a slavesubscriber. The master subscriber is embodied to trigger the dataexchange between the master and the slave subscriber in the form oftelegrams. In this context, the telegrams are realized as scheduledtelegrams having the fixed transmission duration for transmission by atleast one distribution node, and as unscheduled telegrams without thefixed transmission time. Moreover, the master subscriber is embodied togenerate a data header for the unscheduled telegrams to be transmittedto the slave subscriber on the forward run, the data header comprising acontrol section and subsequent to it a separate distribution-node-datafield for each distribution node to be run through. Moreover, thedistribution node generates a data header for the unscheduled telegramsof the slave subscriber to be transmitted to the master subscriber onthe way back, said header comprising a control section and adistribution-node-data field if the unscheduled telegram does notcomprise a data header on the way back. The subsequent distributionnodes supplement the data header of the unscheduled telegram by thedistribution-node-data field assigned to the respective distributionnode for the unscheduled telegrams to be transmitted.

By embodying the subscribers as a master-slave-arrangement, thebus-access rights as well as the telegram throughput of the field-bussystem may be implemented in a simple manner. In this context, themaster subscriber generates the data header of the scheduled or,respectively, unscheduled telegrams that comprises the control sectionand subsequent to it the distribution-node-data field assigned to therespective distribution node. The master subscriber sends the scheduledor unscheduled telegram with the mentioned data header to the respectivedistribution nodes in the automation-communication network, wherein thenumber of individual distribution-node-data fields of the scheduled orunscheduled telegrams informs on the distribution nodes used in theautomation-communication network for telegram transmission. On theforward run, only the master sends scheduled or unscheduled telegramsvia the distribution nodes to the slave. In this way, the masterprevents telegram collisions during transmission as it sends thescheduled or, respectively, unscheduled telegrams to the slaves in acontrolled manner.

On the way back, however, it may occur that in anautomation-communication network in which a plurality of slavesubscribers are arranged, a plurality of slave subscriberssimultaneously transmit unscheduled or, respectively, scheduledtelegrams to the master subscriber which may lead to telegram collisionsin the respective distribution node. However, the respectivedistribution node knows due to the stored information on the scheduledtelegrams, the transmission times of which are usually determined by themaster for the individual distribution nodes, how long a correspondingdata-transmission path to a superordinate distribution node is going tobe free on the way back of the unscheduled telegram. For this reason,the distribution node may examine whether the unscheduled telegram withthe transmission duration may be transmitted within the time slot of thetransmission interface of the distribution node remaining untiltransmission of the next scheduled telegram. If this is not the case,the respective distribution node may fragment the unscheduled telegramon the way back, and provided that the unscheduled telegram does nothave a data header on its way back, generate the data header for theunscheduled telegram. As a result, fragmenting of an unscheduledtelegram is usually on the way back when transmitting the unscheduledtelegram back to the master subscriber.

In the data header of the unscheduled telegram that may correspond tothe above-mentioned control data, the corresponding distribution nodemay deposit the second telegram information in thedistribution-node-data field which may correspond to the above-describeddata field, wherein the second telegram information indicates that thedistribution node has fragmented the unscheduled telegram as well ascomprises the distribution-node identification. The subsequentdistribution nodes supplement the data header by thedistribution-node-data field assigned to the respective distributionnode and the first telegram information in case that the unscheduledtelegram is transmitted in full, and the second telegram information incase that the unscheduled telegram is fragmented, including thedistribution-node identification of the respective distribution node.

The control section of the unscheduled telegram can comprise a lengthinformation of the unscheduled telegram, wherein said length informationof the unscheduled telegram comprises the length of the data header anda length of the user-data block of the unscheduled telegram. Thetransmission duration of the unscheduled telegram is determined by thelength of the unscheduled telegram. In order to fragment the unscheduledtelegram, at first the first distribution node fully receives theunscheduled telegram on the way back to the master subscriber so thatthe length of the unscheduled telegram is known. The subsequentdistribution noes may read the length of the unscheduled telegram fromthe control data of the unscheduled telegram. By the telegram length andthe time slot of the transmission interface remaining until transmissionof the next scheduled telegram by the distribution node, the firstdistribution node may then fragment the unscheduled telegram, whereinthe fragmented unscheduled telegram has a minimum fragment length fortransmitting the fragmented unscheduled telegram. The individualtelegram fragments may vary with regard to telegram length, but are notbelow a minimum fragment length. By inserting the length information inthe front area of the unscheduled telegram, in its control section, thesubsequent distribution nodes may additionally decide at the earliestpossible point in time whether the unscheduled telegram can be fullyforwarded through the respective distribution node or whether it is tobe fragmented by the respective distribution node.

The control section of the unscheduled telegram has a counter indicatingthe number of distribution nodes to be run through by the unscheduledtelegram starting from the master subscriber up to the slave subscriber,or, respectively, the number of distribution nodes to be run through bythe unscheduled telegram starting from the slave subscriber back to themaster subscriber. The distribution node decrements the counter duringthe run of the telegram on the run forward from the master to the slave.Moreover, the distribution node increments the counter during the run ofthe telegram on the way back from the slave to the master. By thecounter in the control section of the unscheduled telegram, eachdistribution node is informed on the number of subsequent distributionnodes during transmission of the unscheduled telegram. In this manner, areliable telegram or, respectively, data transmission may be provided,and it becomes particularly possible to differentiate between the dataheader and user data of the unscheduled telegram.

The scheduled telegrams may be realized as cyclic telegrams, wherein thecyclic telegrams may serve to control an automation system. Moreover,the unscheduled telegrams may be realized as acyclic telegrams.Differentiating between scheduled cyclic telegrams and unscheduledacyclic telegrams may have an advantageous effect on the telegramcirculation in the automation network, as the scheduled cyclic telegramsusually correspond to real-time telegrams that may be relevant forcontrolling the automation system and thus have a fixed transmissiontime for transmission by the at least one distribution node. In contrastthereto, the unscheduled acyclic telegrams corresponding tonon-real-time telegrams do not have a fixed transmission time fortransmission. As a result, unscheduled telegrams may be transmitted inthe time slots in which no scheduled telegrams are sent, withoutaffecting the transmission of the scheduled telegrams.

FIG. 1 shows a schematic structure of an automation-communicationnetwork having a plurality of distribution nodes and network segments.The automation-communication network comprises four distribution nodesCU1, CU2, CU3, CU4, that may be connected to one another via a field busand may have a memory. The topology of the automation-communicationnetwork provides that a first network segment N1 may be connected to afirst input/output interface of the first distribution node CU1. Via afirst data-transmission path D1. The first subscriber may be a mastersubscriber; however, this is not obligatory for the main idea.

Via a second input/output interface as well as via a seconddata-transmission path D2, the first distribution node CU1 is connectedto a fourth network segment N4 comprising a fourth subscriber T4. Apartfrom the shown fourth subscriber T4 in the fourth network segment N4,the fourth network segment N4 may comprise further subscribers. Thefourth subscriber T4 may e.g. be a slave subscriber if theadministrative hierarchy of the automation-communication network is tobe based on the master-slave principle.

A third input/output interface of the first distribution node CU1 and athird data-transmission path D3 serve to connect the first distributionnode CU1 to a first input/output interface of a second distribution nodeCU2. The second distribution node CU2 comprises a second input/outputinterface that is connected to a third distribution node CU3 by a fourthdata transmission path D4 and a first input/output interface. Moreover,the second distribution node CU2 has a third input/output interface thatis connected to a first input/output interface of a fourth distributionnode CU4 via a fifth transmission path D5.

The third distribution node CU3 comprises a second input/outputinterface that is connected to a third network segment N3 by a seventhdata-transmission path D7, the third network segment N3 comprising athird subscriber T3. Instead of the shown third subscriber T3, aplurality of subscribers may be arranged in the third network segmentN3. The third subscriber T3 or the potential plurality of subscribersmay be one or a plurality of slave subscribers.

In addition, the third distribution node CU3 comprises a thirdinput/output interface that is connected to a second network segment N2and a second subscriber T2 arranged therein via a sixthdata-transmission path D6. The second subscriber T2 may e.g. be a slavesubscriber. In addition, the second network segment N2 may comprisefurther subscribers.

By a second input-output interface of the fourth distribution node CU4,the fourth distribution node CU4 may be connected to a sixth networksegment N6 comprising a sixth subscriber T6 by an eighthdata-transmission path 68. The sixth network segment N6 may comprisefurther subscribers. The depicted sixth subscriber T6 may e.g. be aslave subscriber.

A third input/output interface of the fourth distribution node CU4 mayserve to connect the fourth distribution node CU4 to a fifth networksegment N5 and a fifth subscriber T5 by a ninth data-transmission pathD9. The fifth network segment N5 may also comprise a plurality ofsubscribers, as shown in FIG. 1. The fifth subscriber T5 may e.g. be aslave subscriber.

Alternatively, the first to sixth subscriber T1-T6 or one of the firstto sixth subscribers T1-T6 may be a subscriber embodied in a differentmanner; e.g. a standard Ethernet subscriber is conceivable. The datatransmission in the automation-communication network shown in FIG. 1 maybe carried out on the basis of a unified network protocol, e.g. theEtherCAT protocol. In addition, in case of differing embodiments of theindividual subscribers in the network segments, various networkprotocols may be used in the automation-communication network. Themaster subscriber is then embodied in such a way that it may process thevarious network protocols used in the automation-communication network.

The illustration chosen in FIG. 1 with double arrows between the firstto sixth subscriber T1-T6 in the first to sixth network segment N1-N6and the first to fourth distribution node CU1-CU4 indicates that abi-directional data transmission is possible between the first to sixthsubscriber T1-T6 and the first to fourth distribution node CU1-CU4 onthe forward run and on the way back. The first to ninthdata-transmission path D1-D9 between the distribution node CU1-CU4 andsubscribers T1-T6 also comprises a forward run and a way back.Consequently, data may be transmitted in the form of scheduled andunscheduled telegrams between the individual subscribers T1-T6 on aclosed data-transmission path in the automation-communication network.Moreover, the depiction of four distribution nodes CU1, CU2, CU3, CU4 isnot to be considered obligatory as more or less distribution nodes maysimilarly be arranged within the network. Moreover, the number ofindividual input/output interfaces of the distribution nodes may deviatefrom the described number of input/output interfaces. Moreover, it isconceivable to realize the automation-communication network with alarger or smaller number of network segments and/or subscribers.

Subsequently, a data exchange in form of the unscheduled telegramsbetween the first subscriber T1 in the first network segment N1 and thesecond subscriber T2 in the second network N2 is described. In thiscontext, the first subscriber T1 may be a master subscriber and thesecond subscriber T2 may be a slave subscriber. The first subscriber T1puts a data header ahead of each unscheduled EtherCAT telegram in whichthe second subscriber T2 or further non-depicted subscribers in thesecond network segment N2 are to carry out a writing operation in whichthe data are to be written into a user-data field of the unscheduledEtherCAT telegram. This data header contains information for thedistribution nodes CU1, CU2, CU3 arranged between the first and thesecond subscriber T1, T2 in the automation-communication network withregard to forwarding the unscheduled telegrams.

In the exemplary configuration of the automation-communication networkof FIG. 1, three distribution nodes CU1, CU2, CU3 are arranged betweenthe first subscriber T1 of the first network segment N1 and the secondsubscriber T2 of the second network segment N2. According to this, thedata header put ahead of the unscheduled EtherCAT telegram that isgenerated by the first subscriber T1 comprises a separate data sectionfor each distribution node CU1, CU2, CU3 which is in the followingreferred to as data field. The data header of the unscheduled EtherCATtelegram comprises a control section apart from the individual datafields of the distribution nodes CU1, CU2, CU3. The control sectioncomprises an identification information by which a distribution nodeCU1, CU2, CU3 recognizes that the unscheduled telegram is an extendedunscheduled EtherCAT telegram and that it is further assigned a datafield. Moreover, the control section comprises a counter that indicatesthe number of distribution nodes CU1, CU2, CU3 to be run through by theunscheduled telegram starting from the first subscriber T1 up to thesecond subscriber T2 in the second network segment N2. In the shownexample, the counter indicates three distribution nodes CU1, CU2, CU3.Moreover, the control section of the data header comprises a lengthinformation of the unscheduled telegram comprising the entire telegramlength including the data header.

FIGS. 2A and 2B schematically depict the extended unscheduled EtherCATtelegram that apart from the actual EtherCAT telegram further comprisesthe data header for exchanging data between the first subscriber T1shown in FIG. 1 and the second subscriber T2 in the second networksegment N2. FIG. 2A shows the schematic structure of the unscheduledtelegram on the forward run to the second subscriber T2 and FIG. 2Billustrates the schematic telegram structure on the way back, startingfrom the second subscriber T2 to the first subscriber T1 in which theunscheduled telegram is subdivided into fragments. FIG. 2A shows theoutputting of the unscheduled telegram by the first subscriber T1 aswell as after circulation of the unscheduled telegram through theindividual distribution nodes CU1, CU2, CU3 on the forward run of theunscheduled telegram and FIG. 2B shows the telegram structure afterprocessing by the second subscriber T2 and after circulation through thedistribution nodes CU1, CU2, CU3 on the way back.

A first telegram structure TEL1 in FIG. 2A shows the unscheduledtelegram sent by the first subscriber in the first network segment viathe first data-transmission path to the first input/output interface ofthe first distribution node. The unscheduled telegram comprises a firstdata header HEAD1 put ahead of the EtherCAT telegram ECAT. The firstdata header HEAD1 comprises a control section TEL. The control sectionTEL comprises an identification information that indicates an extendedunscheduled EtherCAT telegram. By the identification information, adistribution node may recognize that it is assigned a data field D-CU1,D-CU2, D-CU3. Moreover, the control section TEL comprises a counter. Thecounter indicates the distribution nodes to be run through by theunscheduled telegram. Moreover, the control section TEL comprises alength indication of the unscheduled telegram that indicates the entirelength of the unscheduled telegram, including the first data headerHEAD1.

In the first data header HEAD1, three data fields D-CU1, D-CU2, D-CU3 goalong with the control section TEL, wherein the first data field D-CU1is assigned to the first distribution node, the second data field D-CU2is assigned to the second distribution node and the third data field isassigned to the third distribution node. The individual data fieldsD-CU1, D-CU2, D-CU3 in the first data header HEAD1 of the unscheduledtelegram are as a result arranged in the same order in which theunscheduled telegram passes the individual distribution nodes.

The first distribution node receives the unscheduled telegram asdescribed above and starts to process the unscheduled telegram. Thedistribution node at first evaluates the first data header HEAD1starting with the identification information of the control section TELand recognizes by the identification information that the unscheduledtelegram comprises a first data header HEAD1 put ahead of the EtherCATtelegram, that the unscheduled telegram is an extended EtherCATtelegram. By the counter in the control section TEL of the unscheduledtelegram, the first distribution node recognizes that for transmittingthe unscheduled telegram two further distribution nodes will follow. Forexample, for the number of distribution nodes run through by theunscheduled telegram on the forward run to the second subscriber T2, thecounter shows the value three. In an alternative embodiment of theautomation-communication network of FIG. 1 or in case of another targetsubscriber in a further network segment, the counter may also show adeviating value for the number of distribution nodes to be run through.

The first distribution node reduces (decrements) the counter with thenumber of distribution nodes to be run through to e.g. the value two,and extracts the first data field D-CU1 assigned to the firstdistribution node and following upon the control section TEL from thefirst data header HEAD1 of the unscheduled telegram. After this, thefirst distribution node stores the first data field D-CU1 assigned to itin its memory and forwards the unscheduled telegram shortened by thefirst data field D-CU1 via the third input/output interface of the firstdistribution node. The shortened unscheduled telegram having thetelegram structure TEL2 is shown in FIG. 2A below the first telegramstructure TEL

The information on the first data field D-CU1 deposited by the firstdistribution node in its memory may normally be deleted when theunscheduled telegram has been processed by the first distribution nodeon the way back. In case of losses that may occur when the unscheduledtelegram is transmitted, the memory of the first distribution node mayoverflow. It is then possible to proceed according to the so-called FIFOprinciple (first in, first out) and to delete the oldest information.This procedure is also conceivable in case of information from scheduledtelegrams, for the case that the scheduled telegram arrives very late atthe master subscriber on its way back from the slave subscriber and thecorresponding entry on the information of the first data field D-CU1 inthe memory of the first distribution node has already been deleted. As aresult, the returning scheduled telegram would be treated as a returningunscheduled telegram, which, however, is unproblematic due to thelateness of the scheduled telegram. A conceivable alternative is tointroduce time stamps and to delete the old entries in the memory of thefirst distribution node after expiry of a maximum retaining period.

The second distribution node processes the shortened unscheduledtelegram having the telegram structure TEL2 in analogy to theabove-described processing of the unscheduled telegram having thetelegram structure TEL1. The second distribution node first evaluatesthe second data header HEAD2 put ahead of the EtherCAT telegram ECAT anddetermines by the counter in the control section TEL of the second dataheader HEAD2 that a further distribution node following thereafter isfor transmitting the unscheduled telegram. The second distribution nodethen decrements the counter of the control section TEL in the seconddata header HEAD2 of the unscheduled telegram, e.g. to result in thevalue one, and extracts the second data field D-CU2 assigned to thesecond distribution node from the second data header HEAD2 of theunscheduled telegram. The second data field D-CU2 is arranged betweenthe control section TEL and the third data field D-CU3 in the seconddata header HEAD2 of the unscheduled telegram.

The second distribution node deposits the second data field D-CU2assigned to it in its memory, as described above. Likewise, what wasmentioned above with regard to the duration of information storage mayapply analogously. Moreover, the second distribution node forwards theagain shortened unscheduled telegram with the third telegram structureTEL3 of FIG. 2A via its second input/output interface. The againshortened unscheduled telegram is transmitted to the third distributionnode via the fourth data-transmission path, wherein the thirddistribution node receives the unscheduled telegram on its firstinput/output interface.

When processing the again shortened unscheduled telegram having thethird telegram structure TEL3, the third distribution node proceedsanalogously when processing the shortened unscheduled telegram and theinitially unscheduled telegram of the other two distribution noes. Thethird distribution node at first evaluates the control section TEL ofthe third data header HEAD3 of the again shortened unscheduled EtherCATtelegram. By the counter in the control section TEL, the thirddistribution node recognizes that no further distribution node followsfor transmission of the again shortened unscheduled telegram. As aresult, the third distribution node also extracts, apart from the datafield D-CU3 assigned to it and arranged after the control section TEL inthe third data header HEAD3, the control section TEL from the third dataheader HEAD3 of the telegram. Thereby, the third distribution nodereduces the again shortened unscheduled telegram with the third telegramstructure TEL3 to the EtherCAT telegram ECAT, without data header,having the fourth telegram structure TEL4 shown in FIG. 2A.

The third distribution node stores the third data field D-CU3 assignedto it in its memory. Moreover, the third distribution node depositsanother control information from the EtherCAT telegram ECAT in itsmemory. During storing of the mentioned information, the above-describedmay analogously apply. Said control information may serve to identifythe unscheduled EtherCAT telegram ECAT. It is e.g. possible that thethird distribution node uses the identification information, theso-called “Destination-MAC-ID (DEST-MAC-ID)” comprising the EtherCATtelegram ECAT itself. The Destination-MAC-ID is explained in more detailbelow in conjunction with Table 1. The third distribution nodefurthermore transmits the unscheduled EtherCAT telegram ECAT via itssecond input/output interface and the sixth data-transmission path D6 tothe second network segment having the second subscriber T2.

In the second network segment N2, further subscribers may be arrangedapart from the second subscriber T2 and be configured as slavesubscribers, such as the second subscriber T2. The second input/outputinterface of the third distribution node CU3 forms a closeddata-transmission path having a forward run and a way back inconjunction with the sixth data-transmission path D6 and the secondnetwork segment N2 having the second subscriber T2 as a slavesubscriber. The unscheduled EtherCAT telegram ECAT may be processed bythe slave subscriber during circulation. Usually, processing duringcirculation is carried out on the forward run of the unscheduledEtherCAT telegram ECAT, but may also take place on the way back of theunscheduled EtherCAT telegram ECAT.

The slave subscriber respectively extracts the output data assigned toit by the first subscriber T1 which may be embodied as the mastersubscriber from the unscheduled EtherCAT telegram ECAT and may,depending on the kind of processing (read, write or read/writeoperation) insert input data for the master subscriber. After processingof the unscheduled EtherCAT telegram ECAT by the slave subscriberarranged in the second network segment N2, the third distribution nodeCU3 retrieves the unscheduled EtherCAT telegram ECAT on its secondinput/output interface according to the fourth telegram structure TEL4.

FIG. 2B again shows the unscheduled EtherCAT telegram ECAT with thefourth telegram structure TEL4 as a starting point. The unscheduledEtherCAT telegram ECAT is supplemented with the data header on the wayback of the unscheduled telegram to the first subscriber T1 that may beembodied as a master subscriber, the data header being extended by theindividual distribution notes CU3, CU2, CU1 to be run through one afterthe other in inverted order. For identifying the unscheduled EtherCATtelegram ECAT, the third distribution node CU3 uses, as described above,the identification information which the third distribution node CU3 hasstored on the forward run and which is comprised by the unscheduledEtherCAT telegram ECAT itself.

As it may occur on the way back of the telegram transmission to thefirst subscriber T1 that a plurality of subscribers that may be arrangedin the same or in differing network segments transmit simultaneously,the respective distribution node checks prior to transmission of theunscheduled telegram via the respective data-transmission path to thenext distribution node whether the time slot of the input/outputinterface of the distribution node provided as transmission interface(e.g. the first input/output interface) remaining until transmission ofthe next scheduled telegram is sufficient for transmitting thecorresponding unscheduled telegram. For this purpose, the respectivedistribution node, e.g. the third distribution node CU3, first examinesthe transmission time of the unscheduled telegram to be transmitted. Ifthe third distribution node CU3 receives the complete unscheduledEtherCAT telegram ECAT having the fourth telegram structure TEL4, thelength of the unscheduled telegram from which the transmission time ofthe unscheduled telegram may be learnt is known. Alternatively, thethird distribution node CU3 may determine the length of the unscheduledtelegram from the identification information of the data header of theunscheduled telegram and the stored information via the third data fieldD-CU3, as well. For example, the third distribution node CU3 may forwardthe unscheduled telegram in a cut-through procedure which has theadvantage of less delay during circulation. Complete receipt of theunscheduled telegram by the third distribution node CU3 is absolutelyobligatory if the automation-communication network is not realizedaccording to the master-slave hierarchy and a network protocol deviatingfrom the EtherCAT protocol is used for telegram transmission.

The third distribution node CU3 then generates the fourth data headerHEAD4 and puts it ahead of the unscheduled EtherCAT telegram ECAT. Thefourth data header HEAD4 comprises the control section TEL comprisingthe identification information showing the individual distribution nodesthat the data header of the unscheduled telegram has a data fieldassigned to the respective distribution node. Moreover, theidentification information shows that the unscheduled telegram is anextended EtherCAT telegram ECAT. In addition, the control section TELhas a counter indicating the number of distribution nodes to be runthrough when transmitting the unscheduled telegram back to the firstsubscriber, and the length information providing the entire length ofthe telegram.

If the unscheduled telegram having the time duration can be transmittedwithin the time slot of the transmission interface (the firstinput/output interface) of the distribution node remaining untiltransmission of the next scheduled telegram, e.g. the third distributionnode CU3 inserts a first telegram information into the data field DCU3*of the fourth data header HEAD4 assigned to it, which indicates that thethird distribution node CU3 fully transmits the unscheduled EtherCATtelegram ECAT.

If, however, the unscheduled telegram with the transmission time cannotbe transmitted within the transmission-free time of the transmissioninterface (the first input/output interface) of the distribution node,e.g. the third distribution node CU3 generates a second telegraminformation in the data field D-CU3* assigned to it. The second telegraminformation indicates that the third distribution node CU3 fragments theunscheduled telegram. In addition, the second telegram informationcomprises the distribution-node identification that serves to discernthe individual distribution nodes. The third distribution node CU3fragments the EtherCAT telegram ECAT, wherein the telegram fragmentECAT1 should at least have a minimum fragment length. The schematicstructure of the unscheduled first EtherCAT telegram fragment ECAT1 thatthe third distribution node CU3 sends via its first input/outputinterface to the second input/output interface of the seconddistribution node CU2 may e.g. correspond to the extended fifth telegramstructure TEL5 of FIG. 2B.

In the following Table 1, a possible structure of the fourth data headerHEAD4 with regard to the extended fifth telegram structure TEL5 isshown.

TABLE 1 Byte number Data header section Denotation 0-5 TEL DEST-MAC-ID6-7 TEL TEL-LEN 8 D-CU3* CMD (value 4) 9 D-CU3* FRAME-ID (value X3)10-11 D-CU3* OFFSET (value 0) 12  D-CU3* NEXT (value 1) 13-15 D-CU3*RESERVE

Bytes 0 to 7 of data header HEAD4 are reserved for the control sectionTEL of the telegram. Therein, the bytes 0 to 5 comprise theidentification information DEST-MAC-ID which indicates to the seconddistribution node CU2 that it is an extended unscheduled telegram. Inaddition, the second distribution node CU2 may determine via theidentification information that the data header HEAD4 of the unscheduledtelegram has a data field D-CU3* assigned to the third distribution nodeCU3.

A byte of the identification information DEST-MAC-ID is moreover used asa counter. The counter indicates how many distribution nodes have to berun through, starting from the second subscriber T2 to the firstsubscriber T1, wherein the counter initially has the value one.Furthermore, the bytes 6 and 7 of the control section TEL have a lengthinformation TEL-LEN of the unscheduled telegram, wherein the lengthinformation renders the entire length of the unscheduled telegram(including the data header).

Byte 8 of the data field D-CU3* comprises the second telegraminformation, wherein the second telegram information indicates that thethird distribution node CU3 has fragmented the unscheduled EtherCATtelegram ECAT1. The fragmenting of the unscheduled telegram isidentified by the value CMD=4. Byte 9 of the data field D-CU3* comprisesthe distribution-node identification FRAME-ID of the second telegraminformation, wherein the distribution-node identification FRAME-ID ofthe third distribution node CU3 has the value X3. By thedistribution-node identification, the respective distribution node isidentified. In addition, the distribution-node identification allows forassigning the unscheduled telegram fragments to an EtherCAT telegramECAT as their value is increased for a further unscheduled telegram.

Bytes 10 to 11 of the data field D-CU3* of the second telegraminformation comprise the telegram offset OFFSET, wherein the firstEtherCAT-telegram fragment ECAT1 obtains the offset value=0. Thetelegram offset OFFSET indicates the position of the first user datablock contained in the first EtherCAT-telegram fragment ECAT1, whereinthe user data block may correspond to the above-described user datafield.

Byte 12 of the data field D-CU3* of the second telegram information NEXTindicates that due to fragmentation of the unscheduled EtherCAT telegramECAT1 further telegram fragments are to be transmitted, which ischaracterized by the value NEXT=1.

Bytes 13-15 of the data field C-CU3* RESERVE correspond to reservedbytes that cannot be occupied.

Alternatively, the third distribution node CU3 may transmit theunscheduled EtherCAT telegram to the second distribution node CU2 in anon-fragmented manner and indicate in a first telegram information inthe data field D-CU3* assigned to it that the unscheduled telegram istransmitted in an non-fragmented manner, as well as itsdistribution-node identification X3 that may further be comprised in thefirst telegram information. The structure of the describednon-fragmented telegram is not separately shown in FIG. 2B.

The second distribution node CU2 receives the extended unscheduled firstEtherCAT telegram fragment having the fifth telegram structure TEL5 onits second input/output interface and determines that the unscheduledtelegram comprises a data header HEAD4 put ahead of the actual firstEtherCAT telegram fragment ECAT1 which may be structure according toTable 1. By the stored information of the scheduled telegrams comprisingtheir transmission times, the second distribution node CU2 may determinein connection with the telegram lengths of the scheduled telegramswhether it can immediately forward the unscheduled telegram or whetherthe second distribution node CU2 has to buffer the unscheduled telegram,because from the above-mentioned transmission times and telegram lengthsof the scheduled telegrams, the distribution node may determine the timeslot it may use until an unscheduled telegram is transmitted.

The second distribution node CU2 starts with evaluating the data headerHEAD4, e.g. of the identification information DEST-MAC-ID in the controlsection TEL. The second distribution node CU2 increments the counter byone, so that it indicates the value two and furthermore inserts the datafield D-CU2* assigned to the second distribution node CU2 into the dataheader HEAD5 of the unscheduled telegram fragment ECAT1 between thecontrol section TEL in the data header HEAD5 of the unscheduled telegramfragment ECAT1 and to the data field D-CU3* of the third distributionnode CU3. For example, the remaining time slot of the transmissioninterface (the first input/output interface) of the second distributionnode provided for sending may in the shown example be sufficient fortransmitting the unscheduled first telegram fragment ECAT1 having thesixth telegram structure TEL6 and the transmission time, so that thesecond distribution node CU2 does not have to fragment the firstEtherCAT telegram fragment ECAT1 again. Then, the second distributionnode CU2 indicates that it fully transmits the unscheduled firstEtherCAT telegram fragment ECAT1 by a first telegram information in thedata field D-CU2* of the data header HEAD5 of the second distributionnode. Moreover, the first telegram information may comprise anadditional first EtherCAT telegram fragment ECAT1 in the data fieldD-CU2* of the control section TEL of the unscheduled first EtherCATtelegram fragment ECAT1 in order to allow for an assignment to thesecond distribution node CU2. For example, the distribution-nodeidentification FRAME-ID of the second distribution node CU2 may comprisethe value X2.

The data header HEAD5 of the unscheduled first EtherCAT-telegramfragment ECAT1 having the sixth telegram structure TEL6 which the seconddistribution node CU2 sends to the first distribution node CU1 may e.g.be structured as shown in Table 2.

TABLE 2 Byte number Data header section Denotation 0-5 TEL DEST-MAC-ID6-7 TEL TEL-LEN  8 D-CU2* CMD (value 3)  9 D-CU2* FRAME-ID (value X2)10-15 D-CU2* RESERVE 16 D-CU3* CMD (value 4) 17 D-CU3* FRAME-ID (valueX3) 18-19 D-CU3* OFFSET 20 D-CU3* NEXT (value 1) 21-23 D-CU3* RESERVE

In analogy to Table 1 that describes the structure of data header HEAD4,bytes 0 to 7 are reserved for the control section TEL of the unscheduledfirst telegram fragment ECAT1. Bytes 0 to 5 comprise the identificationinformation DEST-MAC-ID, as described above, one byte of theidentification information DEST-MAC-ID represents the counter and bytes6 to 7 indicate the telegram length TEL-LEN of the first EtherCATtelegram fragment ECAT1.

Byte 8 of the data field D-CU2* comprises the first telegram informationwhich shows by the value CMD=3 that the second distribution node CU2fully transmits the unscheduled first telegram fragment ECAT1 via itsfirst input/output interface to the first distribution node CU1 and doesnot carry out any further fragmentations.

Byte 9 of the data field D-CU2* may in the first telegram informationfurthermore comprise the distribution-node identification FRAME-ID withthe value X2 of the second distribution node CU2.

Bytes 10 to 15 of the data header HEAD5 of the unscheduled firsttelegram fragment ECAT1 having the structure TEL6 may be embodied asreserved bytes RESERVE.

Bytes 16 to 23 may have the structure of data field D-CU3* describedabove in Table 1 and assigned to the third distribution node CU3 and beoccupied in the same way as described in Table 1.

Alternatively, it is conceivable that the second distribution node CU2again fragments the unscheduled first telegram fragment ECAT1 and theninserts additional information into the data header HEAD5 via there-fragmented unscheduled first telegram fragment ECAT1.

The first distribution node CU1 receives the unscheduled first telegramfragment ECAT1 that was sent via the third data-transmission path D3 viaits third input/output interface and proceeds analogously whenevaluating the unscheduled first telegram fragments ECAT1, as the seconddistribution node CU2. The first distribution node CU1 e.g. starts withevaluating the identification information DEST-MAC-ID in the controlsection TEL of the data header HEAD5. The first distribution node CU1increments the counter by one so that it indicates the value three andfurther adds the data field D-CU1* to the data header HEAD6 of theunscheduled telegram fragment ECAT1 assigned to the first distributionnode CU1 between the control section TEL in the data header HEAD5 of theunscheduled telegram fragment ECAT1 and the data field D-CU2* of thesecond distribution node CU2. The again extended unscheduled firstEtherCAT telegram fragment may e.g. have the seventh telegram structureTEL7.

If the first distribution node CU1 again subdivides the re-extendedunscheduled first telegram fragment ECAT1 into e.g. two fragments ECAT2,ECAT3 before forwarding it to the first subscriber T1 in the firstnetwork segment N1, the data header HEAD6 of the re-extended telegramhaving the second telegram fragment ECAT2 and the seventh telegramstructure TEL7 may e.g. be structured as in Table 3.

TABLE 3 Byte number Data header section Denotation 0-5 TEL DEST-MAC-ID6-7 TEL TEL-LEN  8 D-CU1* CMD (value 4)  9 D-CU1* FRAME-ID (value X1)10-11 D-CU1* OFFSET 12 D-CU1* NEXT (value 1) 13-15 D-CU1* RESERVE 16D-CU2* CMD (value 3) 17 D-CU2* FRAME-ID (value X2) 18-23 D-CU2* RESERVE24 D-CU3* CMD (value 4) 25 D-CU3* FRAME-ID (value X3) 26-27 D-CU3*OFFSET 28 D-CU3* NEXT (value 1) 29-31 D-CU3* RESERVE

Bytes 0 to 7 represent the control section TEL of the data header HEAD6of the re-extended unscheduled second telegram fragment ECAT2 having theidentification information DEST-MAC-ID and the length informationTEL-LEN. One byte of the identification information DEST-MAC-ID isprovided analogously to the above-mentioned description for the counter.The counter is set to the value three by the first distribution nodeCU1, as described above.

Byte 8 of data field D-CU1* of the first distribution node CU1 comprisesthe second telegram information. The second telegram informationindicates by the value CMD=4 that the first distribution node CU1 hasdivided up the re-extended first telegram fragment ECAT1 into twofragments ECAT2, ECAT3, wherein at first the second telegram fragmentECAT2 is transmitted and according thereto Table 3 indicates thestructure of the data header HEAD6 of the associated second telegramfragment ECAT2.

Subdividing the re-extended first telegram fragment ECAT1 into twotelegram fragments ECAT2, ECAT3 may e.g. be due to the fact that theremaining time slot of the transmission interface of the firstdistribution node CU1 remaining until the next scheduled telegram istransmitted only suffices for sending a smaller telegram fragment havinga shorter transmission time.

In the second telegram information, byte 9 further comprises thedistribution-node identification FRAME-ID of the first distribution nodeCU1 which has the value X1 and may, as the other distribution-nodeidentifications, be increased with regard to value for each newunscheduled telegram.

Bytes 10 to 11 of the data field D-CU1* of the first telegraminformation comprise the telegram offset OFFSET, which has the telegramoffset OFFSET value n=0.

Byte 12 of the data field D-CU1* NEXT indicates by the value 1 thatfurther telegram fragments ECAT3, ECAT4 still have to be transmitted.

Bytes 13 to 15 form reserved bytes RESERVE that may be unoccupied.

Bytes 16 to 23 are reserved for the data field D-CU2* of the seconddistribution node CU2 and may be structured and occupied analogously tothe above description.

Similarly, bytes 24 to 31 may be occupied and structured in the samemanner as in the above description with regard to data field D-CU3* thatis associated with the third distribution node CU3.

The data header HEAD7 of the third telegram fragment ECAT3 having theeighth telegram structure TEL8 in FIG. 2B may e.g. be structured asshown in Table 4.

TABLE 4 Byte number Data header section Denotation 0-5 TEL DEST-MAC-ID6-7 TEL TEL-LEN  8 D-CU1* CMD (value 4)  9 D-CU1* FRAME-ID (value X1)10-11 D-CU1* OFFSET (value N) 12 D-CU1* NEXT (value 0) 13-15 D-CU1*RESERVE 16 D-CU2* CMD (value 3) 17 D-CU2* FRAME-ID (value X2) 18-23D-CU2* RESERVE 24 D-CU3* CMD (value 4) 25 D-CU3* FRAME-ID (value X3)26-27 D-CU3* OFFSET 28 D-CU3* NEXT (value 1) 29-31 D-CU3* RESERVE

Structure and occupation of bytes 0 to 31 may thereby correspond to thestructure and the occupation of the bytes of data header HEAD6 of thesecond telegram fragment ECAT2 in Table 3. For this reason, thedifferences and the possible differences of byte occupation of dataheader HEAD7 compared to data header HEAD6 are shown for the followingdescription.

Bytes 10 to 11 of data field D-CU1* of the first distribution node CU1comprise the telegram offset OFFSET in the second telegram information.The telegram offset OFFSET may have a value n=N for the data headerHEAD7 of the third telegram fragment ECAT3 as the position of theuser-data block contained in the third telegram fragment ECAT3 maycorrespond to the position N. For comparison, the position of the firstuser-data block contained in the second telegram fragment ECAT2corresponds to the value n=0.

A possible difference of the structure of the data header HEAD7 comparedto the structure of data header HEAD6 may be in bytes 6 to 7 of Table 4.Bytes 6 to 7 indicate the telegram length TEL-LEN, including the dataheader HEAD7. It is possible that the third telegram fragment ECAT3differs from the second telegram fragment ECAT2 with regard to length.As a result, the value for the telegram length TEL-LEN may vary for thethird unscheduled telegram fragment ECAT3 in Table 4.

Alternatively, it is possible that the first distribution node CU1 doesnot fragment the unscheduled first telegram fragment ECAT1 received fromthe distribution node CU2 before the first distribution node forwardsthe telegram to the first subscriber of the first network segment. Here,receipt of the unscheduled first telegram fragment ECAT1 and evaluationof the associated data header of the unscheduled first telegram fragmentECAT1 may take place analogously to the procedure described above inconjunction with the receipt of the unscheduled second telegram fragmentECAT2 having the seventh telegram structure TEL7 by the firstdistribution node. The structure of the not further fragmented firsttelegram fragment ECAT1 may be sent from the first distribution node CU1via its first input/output interface to the first subscriber T1 in thefirst network segment N1. The data header of the not re-fragmentedtelegram fragment ECAT1 may be structured according to Table 5.

TABLE 5 Byte number Data header section Denotation 0-5 TEL DEST-MAC-ID6-7 TEL TEL-LEN  8 D-CU1* CMD (value 3)  9 D-CU1* FRAME-ID (value X1)10-15 D-CU1* RESERVE 16 D-CU2* CMD (value 3) 17 D-CU2* FRAME-ID (valueX2) 18-23 D-CU2* RESERVE 24 D-CU3* CMD (value 4) 25 D-CU3* FRAME-ID(value X3) 26-27 D-CU3* OFFSET 28 D-CU3* NEXT (value 1) 29-31 D-CU3*RESERVE

In analogy to the other Tables 1 to 4, bytes 0 to 7 are reserved forcontrol section TEL of the data header. They comprise the identificationinformation DEST-MAC-ID as well as a byte of the DEST-MAC-ID comprisingthe counter. The control section TEL furthermore comprises, in bytes 6to 7, the length TEL-LEN of the first telegram fragment ECAT1 that hasnot been further fragmented.

Byte 8 of the data field D-CU1* comprises the first telegraminformation. In the first telegram information, the first distributionnode CU1 characterizes by the allocation CMD=3 that it fully transmitsthe first telegram fragment ECAT that has not been further fragmented tothe first subscriber. In this context, the first telegram informationmay further comprise the distribution-node identification FRAME-ID ofthe first distribution node having the value X1 in the byte 9.

Bytes 10 to 15 of the data field D-CU1* may be provided as reservedbytes RESERVE.

Moreover, bytes 16 to 23 for data field D-CU2* of the seconddistribution node CU2 as well as bytes 24 to 31 for the data fieldD-CU3* of the third distribution node CU3 may be occupied in analogy tothe above description, in which the third distribution node CU3fragments the unscheduled EtherCAT telegram ECAT and the seconddistribution node CU2 forwards the first telegram fragment ECAT1 to thefirst distribution node CU1 without renewed fragmentation.

After transmitting the third EtherCAT telegram fragment ECAT1 to thefirst subscriber T1 by the first distribution node CU1, e.g. the fourthEtherCAT telegram fragment ECAT4 having the telegram structure TEL9 andthe data header HEAD8 may be transmitted by the first distribution nodeCU1 to the first subscriber T1, the master subscriber, in the firstnetwork segment N1. In order to avoid repetitions, it is assumed thatthe fourth EtherCAT telegram fragment ECAT4 was transmitted analogouslyto the above description with regard to the first EtherCAT telegramfragment ECAT1 by the third distribution node CU3 to the seconddistribution node CU2 and from the second distribution node CU2 to thefirst distribution node CU1. In contrast to the previous description,the fourth EtherCAT telegram fragment ECAT4 is not again fragmentedduring transmission by the second distribution node CU2 to the firstdistribution node CU1. As a result, the telegram structure TEL9 shown inFIG. 2B is provided during transmission of the fourth EtherCAT telegramfragment ECAT4 from the first distribution node CU1 to the firstsubscriber T1. Thereby, the same input/output interfaces of thedistribution nodes that are provided as the respective transmissioninterfaces of the distribution nodes may be used for the transmission ofthe unscheduled fourth telegram fragment ECAT4, as described above.

The fourth EtherCAT telegram fragment ECAT4 may e.g. correspond to thecounterpart of the first EtherCAT telegram fragment ECAT1 and, togetherwith the unscheduled first EtherCAT telegram fragment ECAT1 that wasfragmented to result in second and third telegram fragments ECAT2,ECAT3, form the complete unscheduled EtherCAT telegram fragment ECAT.For example, the time slot for transmitting the fourth EtherCAT telegramfragment ECAT4 by the third, second and first distribution node maysuffice in order to fully transmit the unscheduled fourth telegramfragment ECAT4 having the telegram structure TEL9 of FIG. 2B to themaster subscriber. The distribution nodes characterize the fulltransmission of the fourth telegram fragment ECAT4 by the first telegraminformation, in analogy to the above description. Alternatively, renewedfragmenting or, respectively, multiple fragmenting of the unscheduledfourth telegram fragment ECAT4 for transmission is conceivable. Therespective distribution node further fragmenting the unscheduled fourthEtherCAT telegram fragment ECAT4 then deposits the fragmentation of thefourth telegram fragment ECAT4 in the second telegram information asdescribed above together with the distribution-node identification.Here, a description of the occupation of the individual bytes for thedata header HEAD8 of the unscheduled fourth telegram fragments ECAT4having the telegram structure TEL9 according to Tables 1 to 5 is notgiven since the occupation of the bytes of the data header HEAD8 may becarried out in a comparable manner as in the previous tables.

The first subscriber T1 in the first network segment N1 that may e.g. beconfigured as a master subscriber has to reassemble the telegramfragments to result in a complete telegram. Alternatively, the first,second and/or third distribution node CU1, CU2 and/or CU3 may reassemblethe individual telegram fragments that have e.g. accumulated in theirmemories due to the respective data-transmission paths being occupied.This procedure may furthermore contribute to an efficient datatransmission, as less data headers have to be transmitted.

The first subscriber T1 or, respectively, the master subscriberrecognizes the telegram fragments belonging to an unscheduled EtherCATtelegram by the distribution-node identifications FRAME-IDs of all datafields D-CU1*, D-CU2*, D-CU3* of the distribution nodes in the dataheader of the unscheduled telegrams being identical for all telegramfragments. In the shown embodiment example, the distribution-nodeidentifications FRAME-IDs of the data fields D-CU1*, D-CU2*, D-CU3* ofthe distribution nodes have the values X1 (first distribution node), X2(second distribution node) and X3 (third distribution node) for theabove-described first to fourth telegram fragments ECAT1-ECAT4. In a newunscheduled telegram, the values of the distribution-nodeidentifications FRAME-IDs would deviate from the stated values and thusallow for identifying said unscheduled EtherCAT telegram ECAT and forassigning possible first to fourth telegram fragments ECAT1-ECAT4 of theEtherCAT telegram ECAT.

The above-described data exchange is optimized for the EtherCATprotocol. For the EtherCAT protocol, it is necessary to remove the dataheader of the scheduled or, respectively, unscheduled telegram as theslave subscriber being the recipient of the scheduled or, respectively,unscheduled telegram is not able to process this part of the scheduledor, respectively, unscheduled telegram. For this reason, the data headerof the distribution nodes to be run through on the forward run isgradually removed from the unscheduled telegram and respectivelybuffered, in order to be inserted into the unscheduled telegram on itsway back and to be extended with additional information. Thereby, themaster subscriber or the respective distribution nodes may generate thedata header. Alternatively, it is conceivable that the slave subscriberis able to generate the data header of the unscheduled telegram.

The procedure may also be used in such distribution nodes that are e.g.embodied as switches in which the transmission time of the scheduledcyclic telegram is set via a configuration phase in the distributionnodes. In this manner, the throughput of unscheduled acyclic telegramsmay be increased as a part of the unscheduled telegram, an unscheduledtelegram fragment; however, the complete unscheduled telegram may or maynot be transmitted before the acyclic phase has ended.

Furthermore, it is possible to use automation-communication networksthat are not structured according to the master-slave-administrationprinciple. All automation-communication networks may be used in which afirst subscriber is arranged in a first network segment, a secondsubscriber in a second network segment and at least a distribution nodeis arranged between the two subscribers and a telegram or, respectively,data transmission is to take place between these two subscribers.

If a different protocol is used for exchanging data instead of theEtherCAT protocol in which the slave subscriber(s) may process the dataheader, it is not necessary for the distribution nodes to remove theassociated data field from the data header of the unscheduled telegramon the forward run of the unscheduled telegram to the slave subscriberor the slave subscribers. Alternatively, only the last distribution nodemay be embodied to remove the data fields of the distribution nodes fromthe data header of the unscheduled telegram, whereby this possibilitymay become obsolete if the slave subscriber(s) are able to process thedata header of the unscheduled telegram. In both mentioned cases, thedata header remains at the unscheduled telegram and may be evaluated bythe distribution nodes and be forwarded together with the unscheduledtelegram.

Furthermore, it is conceivable to use a correspondingly configuredprotocol for exchanging data as well as correspondingly embodied slavesubscribers in the automation-communication network that may process thedata header of the unscheduled telegram and insert the evaluation of thedata header into the new unscheduled telegram that they send back to themaster subscriber.

In some embodiments, in an automation-communication network, at leastone distribution node is provided. The distribution node comprises aplurality of input/output interfaces that are each connected to at leastone network segment, wherein in a first network segment a firstsubscriber and in a second network segment a second subscriber arearranged. Data are exchanged between the first and the second subscriberby telegrams, wherein the telegrams are realized as scheduled telegramshaving a fixed transmission time for transmitting via the distributionnode, and as unscheduled telegrams without a fixed transmission time fortransmitting via the distribution node. The unscheduled telegrams eachcomprise control data for the distribution node and these in turncomprise a data field that is processed by the distribution node. Thedistribution node is configured to receive an unscheduled telegram on aninput/output interface and to send an unscheduled telegram on a furtherinput/output interface. Furthermore the distribution node is configuredto determine a transmission duration for transmission of the unscheduledtelegram. Moreover the distribution node is configured to determine atime slot of the input/output interface provided as the transmittinginterface for the unscheduled telegram, said time slot remaining until anext scheduled telegram is transmitted, and to examine whether theunscheduled telegram with said transmitting duration can be transmittedwithin the remaining time slot. The distribution node is also configuredto transmit the unscheduled telegram via the transmission interface ifthe unscheduled telegram with said transmission duration can betransmitted within the remaining time slot of the transmission interfaceup until transmission of a next scheduled telegram. Prior totransmission, the distribution node deposits a first telegraminformation in the data field of the control data, said telegraminformation indicating complete transmission of the unscheduledtelegram. The distribution node fragments the unscheduled telegram ifthe telegram with the transmission duration cannot be transmitted withinthe remaining time slot of the transmission interface up untiltransmission of the next scheduled telegram. Furthermore, prior totransmission of the unscheduled telegram, the distribution node enters asecond telegram information into the data field of the control data ofthe unscheduled telegram that indicates that the telegram is going to befragmented and comprises an additional distribution-node identificationthat serves to discern the individual distribution nodes in theautomation-communication network.

The present invention is described in detail in context with preferredembodiments and examples. Further embodiments and examples arecontemplated that may comprise modifications or combinations of thedescribed features. For this reason, the present invention is notlimited to the disclosed examples, as a person skilled in the art maydevise other variations without exceeding the scope of protection of thepresent invention as claimed.

The advantageous embodiments of the invention described above and/orindicated in the claims may be used individually or in any desiredcombination with one another—except e.g. in cases of expressly reciteddependencies and alternatives.

1. A method for transmitting data in an automation-communication networkcomprising at least one distribution node having a plurality ofinput/output interfaces that are each connected to at least one networksegment, wherein in a first network segment a first subscriber and in asecond network segment a second subscriber are arranged; wherein dataare exchanged between the first subscriber and the second subscriber inthe form of telegrams; wherein the telegrams are realized as scheduledtelegrams characterized by a fixed transmission time for transmittingvia the at least one distribution node and as unscheduled telegramscharacterized by not having a fixed transmission time for transmittingvia the at least one distribution node; wherein the unscheduledtelegrams are each assigned control data for the distribution node andthe control data comprise a data field that is processed by thedistribution node; wherein the distribution node is configured toreceive an unscheduled telegram on an input/output interface and to sendan unscheduled telegram on a further input/output interface; wherein thedistribution node is configured to determine a transmission duration fortransmitting the unscheduled telegram; wherein the distribution node isconfigured to determine a time slot of the input/output interfaceprovided as the transmitting interface for the unscheduled telegram,said time slot remaining until a next scheduled telegram is transmitted,and to examine whether the unscheduled telegram with said transmittingduration can be transmitted within the remaining time slot; wherein thedistribution node transmits the unscheduled telegram via thetransmission interface if the unscheduled telegram with saidtransmission duration can be transmitted within the remaining time slotof the transmitting interface until the next scheduled telegram istransmitted; wherein the distribution node enters a first telegraminformation prior to the transmission of the unscheduled telegram intothe data field of the control data of the unscheduled telegram; whereinthe first telegram information indicates that the unscheduled telegramis fully transmitted; wherein the distribution node fragments theunscheduled telegram if the telegram with the transmission durationcannot be transmitted within the remaining time slot of the transmissioninterface up until transmission of the next scheduled telegram; whereinthe distribution node enters a second telegram information in the datafield of the control data of the unscheduled telegram prior totransmitting the unscheduled telegram; and wherein the second telegraminformation indicates that the telegram is going to be fragmented andcomprises an additional distribution-node identification that serves todiscern the individual distribution nodes in theautomation-communication network.
 2. The method according to claim 1,wherein a plurality of distribution nodes is arranged between the firstsubscriber and the second subscriber; wherein a separate data field ofthe control data of the unscheduled telegram is assigned to eachdistribution node which is independently processed by the respectivedistribution node; wherein the respective distribution node fragmentsthe unscheduled telegram that is transmitted from the second subscriberto the first subscriber if the unscheduled telegram with the respectivetransmission duration cannot be transmitted within the remaining timeslot of the transmission interface up until transmission of the nextscheduled telegram by the respective distribution node; wherein therespective distribution node enters a second telegram information in theassigned data field of the control data of the unscheduled telegramprior to transmitting the unscheduled telegram; wherein the secondtelegram information indicates that the unscheduled telegram is going tobe fragmented and comprises an additional distribution-nodeidentification; and wherein the respective distribution node transmitsthe unscheduled telegram in fragments.
 3. The method according to claim1, wherein the distribution-node identification of the second telegraminformation allows for additional assigning to the correspondingunscheduled telegram; and wherein the distribution-node identificationof the second telegram information is incremented for a new unscheduledtelegram.
 4. The method according to claim 1, wherein the respectivedistribution node inserts a telegram offset into its assigned data fieldof the control data of the unscheduled telegram, in the second telegraminformation, if the respective distribution node fragments theunscheduled telegram; wherein the telegram offset indicates a value ncomprising a position of a first user-data block contained in theunscheduled telegram; and wherein the first telegram fragmentparticularly comprises the telegram-offset value n=0.
 5. The methodaccording to claim 1, wherein the respective distribution node depositsin its assigned data field of the control data of the unscheduledtelegram, in the second telegram information, that further telegramfragments are to be transmitted if the respective distribution nodefragments the unscheduled telegram.
 6. The method according to claim 1,wherein the telegrams are transmitted on a closed data-transmission pathoriginating from the first subscriber to the second subscriber on itsforward run, and back, originating from the second subscriber to thefirst subscriber on the return; wherein the first subscriber arranged inthe first network segment is realized as a master subscriber; andwherein the second subscriber arranged in the second network segment isrealized as a slave subscriber; wherein the data exchange between themaster subscriber and the slave subscriber is triggered by the mastersubscriber in the form of the telegrams; wherein the telegrams arerealized as the scheduled telegrams with a fixed transmission time fortransmission by the at least one distribution node and as theunscheduled telegrams without a fixed transmission time; wherein themaster subscriber generates a data header for the transmittedunscheduled telegrams to be transmitted to the slave subscriber on theforward run, the data header comprising a control section and subsequentthereto a separate distribution-node-data field for each distributionnode to be run through; wherein the distribution node generates a dataheader for the unscheduled telegrams of the slave subscriber to betransmitted on the way back to the master subscriber, the data headercomprising a control section and a distribution-node-data field, if theunscheduled telegram does not comprise a data header on its way back;and wherein the subsequent distribution nodes supplement the data headerfor the unscheduled telegrams to be transmitted by the distribution-nodedata field assigned to the respective distribution node.
 7. The methodaccording to claim 1, wherein the control section of the unscheduledtelegram comprises an indication of length of the unscheduled telegram;and wherein the indication of length of the unscheduled telegramcomprises the length of the data header and a length of the user-datablock of the unscheduled telegram.
 8. The method according to claim 1,wherein the control section of the unscheduled telegram comprises acounter that, starting from the master subscriber, indicates the numberof distribution nodes to be run through by the unscheduled telegram upuntil the slave subscriber or, respectively, starting from the slavesubscriber, the number of distribution nodes to be run through by theunscheduled telegrams up until the master subscriber; wherein thedistribution node decrements the counter during circulation of thetelegrams on the forward run from the master subscriber to the slavesubscriber; and wherein the distribution node increments the counterduring circulation of the telegrams on the way back from the slavesubscriber to the master subscriber.
 9. The method according to claim 1,wherein the scheduled telegrams are realized as cyclic telegrams servingto control an automation system; and wherein the unscheduled telegramsare realized as acyclic telegrams.
 10. An automation-communicationnetwork having at least one distribution node comprising a plurality ofinput/output interfaces that are each connected to at least one networksegment, wherein in a first network segment a first subscriber and in asecond network segment a second subscriber are arranged, wherein dataare exchanged between the first subscriber and the second subscriber inthe form of telegrams; wherein the telegrams are realized as scheduledtelegrams characterized by a fixed transmission time for transmittingvia the at least one distribution node and as unscheduled telegramscharacterized by not having a fixed transmission time for transmittingvia the at least one distribution node; wherein the unscheduledtelegrams are each assigned control data for the distribution node andthe control data comprise a data field that is processed by thedistribution node; wherein the distribution node is configured toreceive an unscheduled telegram on an input/output interface and to sendan unscheduled telegram on a further input/output interface; wherein thedistribution node is configured to determine a transmission duration fortransmission of the unscheduled telegram; wherein the distribution nodeis configured to determine a time slot of the input/output interfaceprovided as the transmitting interface for the unscheduled telegram,said time slot remaining until a next scheduled telegram is transmitted,and to examine whether the unscheduled telegram with said transmittingduration can be transmitted within the remaining time slot; wherein thedistribution node is configured to transmit the unscheduled telegram viathe transmission interface if the unscheduled telegram with saidtransmission duration can be transmitted within the remaining time slotof the transmitting interface until the next scheduled telegram istransmitted; wherein the distribution node is configured to enter afirst telegram information prior to the transmission of the unscheduledtelegram into the data field of the control data of the unscheduledtelegram; wherein the first telegram information indicates that theunscheduled telegram is fully transmitted; wherein the distribution nodeis configured to fragment the unscheduled telegram if the telegram withthe transmission duration cannot be transmitted within the remainingtime slot of the transmission interface up until transmission of thenext scheduled telegram; wherein the distribution node is configured toenter a second telegram information in the data field of the controldata of the unscheduled telegram prior to transmitting the unscheduledtelegram; and wherein the second telegram information indicates that thetelegram is going to be fragmented and comprises an additionaldistribution-node identification that serves to discern the individualdistribution nodes in the automation-communication network.
 11. Theautomation-communication network according to claim 10, wherein betweenthe first subscriber and the second subscriber a plurality ofdistribution nodes is arranged; wherein a separate data field of thecontrol data of the unscheduled telegram is assigned to eachdistribution node which is independently processed by the respectivedistribution node; wherein the respective distribution node isconfigured to fragment the unscheduled telegram that is transmitted fromthe second subscriber to the first subscriber if the unscheduledtelegram with the respective transmission duration cannot be transmittedwithin the remaining time slot of the transmission interface up untiltransmission of the next scheduled telegram by the respectivedistribution node, and wherein the respective distribution node isconfigured to enter a second telegram information in the assigned datafield of the control data of the unscheduled telegram; wherein thesecond telegram information indicates that the telegram is going to befragmented and comprises an additional distribution-node identification;and wherein the respective distribution node transmits the unscheduledtelegram in fragments.
 12. The automation-communication networkaccording to claim 10, wherein the distribution-node identification ofthe second telegram information allows for additional assigning of thecorresponding unscheduled telegram; and wherein the distribution node isconfigured to increment the distribution-node identification of thesecond telegram information for a new unscheduled telegram.
 13. Theautomation-communication network according to claim 10, wherein therespective distribution node is configured to note a telegram offset inthe assigned data field of the control data of the unscheduled telegram,in the second telegram information, if the respective distribution nodefragments the unscheduled telegram; wherein the telegram offsetindicates a value n which comprises a position of a first user-datablock contained in the unscheduled telegram; and wherein the firsttelegram fragment particularly has the telegram-offset value n=0. 14.The automation-communication network according to claim 10, wherein therespective distribution node is configured to deposit in its assigneddata field of the control data of the unscheduled telegram, in thesecond telegram information, that further telegram fragments are to betransmitted if the respective distribution node fragments theunscheduled telegram.
 15. The automation-communication network accordingto claim 10, wherein the telegrams are transmitted on a closeddata-transmission path originating from the first subscriber to thesecond subscriber on its forward run, and back, originating from thesecond subscriber to the first subscriber on the return; wherein thefirst subscriber arranged in the first network segment is realized as amaster subscriber; and wherein the second subscriber arranged in thesecond network segment is realized as a slave subscriber; wherein themaster subscriber is configured to trigger the data exchange between themaster subscriber and the slave subscriber in the form of the telegrams;wherein the telegrams are realized as the scheduled telegrams with afixed transmission time for transmission by the at least onedistribution node and as the unscheduled telegrams without a fixedtransmission time; wherein the master subscriber is configured togenerate a data header for the transmitted unscheduled telegrams to betransmitted to the slave subscriber on the forward run, the data headercomprising a control section and subsequent thereto a separatedistribution-node-data field for each distribution node to be runthrough; wherein the distribution node is configured to generate a dataheader for the unscheduled telegrams of the slave subscriber to betransmitted on the way back to the master subscriber, the data headercomprising a control section and a distribution-node-data field, if theunscheduled telegram does not comprise a data header on its way back;and wherein the subsequent distribution nodes are configured tosupplement the data header for the unscheduled telegrams to betransmitted by the distribution-node data field assigned to therespective distribution node.
 16. The automation-communication networkaccording to claim 10, wherein the control section of the unscheduledtelegram comprises an indication of length of the unscheduled telegram;and wherein the indication of length of the unscheduled telegramcomprises the length of the data header and a length of the user-datablock of the unscheduled telegram.
 17. The automation-communicationnetwork according to claim 10, wherein the control section of theunscheduled telegram comprises a counter that, starting from the mastersubscriber, indicates the number of distribution nodes to be run throughby the unscheduled telegram up until the slave subscriber or,respectively, starting from the slave subscriber, indicates the numberof distribution nodes to be run through by the unscheduled telegrams upuntil the master subscriber; wherein the distribution node is configuredto decrement the counter during circulation of the telegrams on theforward run from the master subscriber to the slave subscriber; andwherein the distribution node is configured to increment the counterduring circulation of the telegrams on the way back from the slavesubscriber to the master subscriber.
 18. The automation-communicationnetwork according to claim 10, wherein the scheduled telegrams arerealized as cyclic telegrams serving to control an automation system;and wherein the unscheduled telegrams are realized as acyclic telegrams.19. A distribution node for an automation-communication network, whereinthe distribution node having a plurality of input/output interfaces thatare each connected to at least one network segment, wherein in a firstnetwork segment a first subscriber and in a second network segment asecond subscriber are arranged; wherein data are exchanged between thefirst subscriber and the second subscriber in the form of telegrams;wherein the telegrams are realized as scheduled telegrams characterizedby a fixed transmission time for transmitting via the at least onedistribution node and as unscheduled telegrams characterized by nothaving a fixed transmission time for transmitting via the at least onedistribution node; wherein the unscheduled telegrams are each assignedcontrol data for the distribution node and the control data comprise adata field that is processed by the distribution node; wherein thedistribution node is configured to receive an unscheduled telegram on aninput/output interface and to send an unscheduled telegram on a furtherinput/output interface; wherein the distribution node is configured todetermine a transmission duration for transmitting the unscheduledtelegram; wherein the distribution node is configured to determine atime slot of the input/output interface provided as the transmittinginterface for the unscheduled telegram, said time slot remaining until anext scheduled telegram is transmitted, and to examine whether theunscheduled telegram with said transmitting duration can be transmittedwithin the remaining time slot; wherein the distribution node transmitsthe unscheduled telegram via the transmission interface if theunscheduled telegram with said transmission duration can be transmittedwithin the remaining time slot of the transmitting interface until thenext scheduled telegram is transmitted; wherein the distribution nodeenters a first telegram information prior to the transmission of theunscheduled telegram into the data field of the control data of theunscheduled telegram; wherein the first telegram information indicatesthat the unscheduled telegram is fully transmitted; wherein thedistribution node fragments the unscheduled telegram if the telegramwith the transmission duration cannot be transmitted within theremaining time slot of the transmission interface up until transmissionof the next scheduled telegram; wherein the distribution node enters asecond telegram information in the data field of the control data of theunscheduled telegram prior to transmitting the unscheduled telegram; andwherein the second telegram information indicates that the telegram isgoing to be fragmented and comprises an additional distribution-nodeidentification that serves to discern the individual distribution nodesin the automation-communication network.
 20. The distribution nodeaccording to claim 19, wherein a plurality of distribution nodes isarranged between the first subscriber and the second subscriber; whereina separate data field of the control data of the unscheduled telegram isassigned to each distribution node which is independently processed bythe respective distribution node; wherein the respective distributionnode fragments the unscheduled telegram that is transmitted from thesecond subscriber to the first subscriber if the unscheduled telegramwith the respective transmission duration cannot be transmitted withinthe remaining time slot of the transmission interface up untiltransmission of the next scheduled telegram by the respectivedistribution node; wherein the respective distribution node enters asecond telegram information in the assigned data field of the controldata of the unscheduled telegram prior to transmitting the unscheduledtelegram; and wherein the second telegram information indicates that theunscheduled telegram is going to be fragmented and comprises anadditional distribution-node identification; wherein the respectivedistribution node transmits the unscheduled telegram in fragments. 21.The distribution node according to claim 19, wherein the respectivedistribution node is configured to note a telegram offset in theassigned data field of the control data of the unscheduled telegram, inthe second telegram information, if the respective distribution nodefragments the unscheduled telegram; wherein the telegram offsetindicates a value n which comprises a position of a first user-datablock contained in the unscheduled telegram; and wherein the firsttelegram fragment particularly has the telegram-offset value n=0. 22.The distribution node according to claim 19, wherein the respectivedistribution node deposits in its assigned data field of the controldata of the unscheduled telegram, in the second telegram information,that further telegram fragments are to be transmitted if the respectivedistribution node fragments the unscheduled telegram.